Method of breaking foam



` Febill 1941- w. E. MccoRQUonALE. JR., Erm. 2,231544 METHOD OF BREAKINGFOAMl IFiled June 16, 1958 Patented Feb. 1l, 1941 UNITED' STATES METHODF BREAKING FOAM Wilmer E. McCorquodale, Jr., Ardentown, Del., ,andCharles H. Brooks, Swarthmore, Pa., as-

signors to Sun Oil Company, Philadelphia, Pa., a corporation of NewJersey Application June 16,

6 Claims.

In the refining of petroleum, emulsions of water in heavy oil or asphaltare very often formed which are extremely difficult to break, and willnot separate on standing. Such emulsions are most difficult to breakwhen there is present in the oil or asphalt, as the case may be, even asmall percentage of protective materials, such as so-called petroleumacids, as these acids, or their soaps if the oil has been treated withan alkali,

tend to cause the water and oil to form extremely stable emulsions.

Such emulsions cannot be broken by merely heating the emulsionssumciently to vaporize the water since when this is attempted, thevaporizav tion of the water causes the formation of foam which can bebroken down only with great difiiculty. Therefore various otherprocedures for dehydrating such emulsions have heretofore been proposed,among which may be mentioned the I method of heating such emulsionsunder a pressure sufficient to prevent vaporization of the water andthen permitting the water and oil of suchga heated emulsion to separatewhile under pressure,'it having been found that heat and. pressure willeiect a break of the emulsion or a separation of the component partsthereof from each other. Such a procedure has to usually'be car.- riedout as a batch process although attempts have been made to carry it outcontinuously, but in such cases extremely large settling tanks arenecessary and their control is diflicult. The use of a pressuresufciently high to prevent vaporization of the water is an essentialfeature of such a process since, if such pressure is not employed,

' 35 the vaporization of water which results causes the formation offoam which prevents the separation of the component parts of theemulsion and also practically prevents further heating of the emulsion.i i Wehave discovered that such foam can easily be broken and that suchemulsions can be broken in a continuous manner so as to substantiallycompletely dehydrate the oil or asphalt.

In carrying out the present invention, the emul- 45 sion is heated to atemperature above the boiling point of water, but is maintained duringheating under a pressure sumciently high to prevent vaporization of thewater. A fter the emulsion has -been heated sufciently, it is expandedinto a zone at a pressure above the final pressure, but sufciently belowthe initial heating pressure to permit all of the water to be vaporized.This expansion causes the formation of foam which is broken down only-very slowly merely by per- 55 mitting it to stand. We have found thatif the foam thus formed is then expanded under the conditionshereinafter set forth through an orice sufliciently small to completelybreak up the foam, it readily separates into its component parts, oil

and steam.

193s, serial No. 214,144 (C1. 252-321) In the mmm heating step sumcientheat isvv preferably supplied to the emulsion, in the form of specicheat, to furnish the latent heat of vaporization necessary to evaporateall of the water present on the Afirst expansion step, since, if this isnot followed out and any water is left in the foam, it is apparent thaton further expansion through the orifice, the water unvaporized in thefirst pressure reduction step may be vaporized by the further drop inpressure through the orice, and prevent the breaking up l of the foam.It is also highly desirable during the initial heating step that theemulsion be maintained under sufcient pressure to prevent vaporizationof any of the waterv present since, although the foam which may beformed by the vaporization of the water is broken by expansion throughthe orifice as above set forth, lthe formation of foamduring the heatingstep renders further heating of the emulsion very diflicult. 1

This is true since an emulsion containing. a substantial amount of foamabsorbs heat only very slowly.

It is, therefore, an object of the present invention to provide a methodof breaking foam.

A further object of the invention is to provide a method for dehydratingsolutions of viscous liquids which tend to form foam.

For a better understanding of the invention, reference should be made tothe accompanying drawing the single figure of which is a diagrammaticowv chart of apparatus suitable for practicing the invention.

The emulsion which it is desired to break or dehydrate is stored ina`tank'i and is removed therefrom through line 2 by pump 3 andforcedunder sufficient pressure to prevent vaporizaton through a heaterll, wherein it is heated to the desired degree. heater 4 passes througha pressure reducing valve 5 into an enlarged `conduit or vaporizing zone6 the pressure being reduced siimciently in the zone G to permit thewater contained therein to vaporize. 'Ihe vaporization of the .watercauses the formation of foam in the zone 6 which flows to the sprayheads or orice plates 8 in tank 9. Each spray head or orifice plate 8 isprovided with a number of small orifices through which the foam Theheated emulsion from the passes, a pressure diierential of 2 to 14 lbs.per

square inch being maintained between expansion zone 6 and the tank 9 therate of flow and consequent pressure drop across the orices beingcontrolled by using only a suillcient number of the therefrom throughvalved line H. As a general rule, the pressure maintained in tank 9 isatmospheric pressure though, if desired, a higher pressure may bemaintained therein with a correspondingly higher pressure beingmaintained in expansion zone 6.

As a specific example, asphaltic still bottoms containing dissolved and/or suspended Water from tank I were heated in heater 4 to a temperatureof about 365 F. under a pressure of 175 pounds per square inch. Theheated still bottoms were then passed through a pressure release valve 5into expansion zone 6 and the pressure thereon reduced to between 2-14pounds per square inch above atmospheric pressure. This reduction inpressure permitted all the water remaining in the still bottoms tovaporize. The steam, however,

broke up the still bottoms and formed with them a nely divided foamwhich was not readily broken down merely by permitting it to stand, dueto the surface tension of the still bottoms and the fact that on coolingthey became substantially solid. This foam, sitill in a heatedcondition, was then expanded through the orices in orifice plate 8 intotank 9 and the pressure dropped to substantially atmospheric pressure,the expansion through the orices causing the minute bubbles forming thefoam to break up and separate into steam and liquid dehydrated stillbottoms. It has been found that for heavy oils, with the drop inpressure of from 2-14 pounds per square inch across the orifices, anorifice not larger than 1A" is required. 'Ihese conditions were found tobe particularly suitable Where oil mixtures containing from 1.6-3.7 percent of water were treated.

It is to be understood that the apparatus and specific example justdescribed are illustrative only of the invention and that variouschanges and modifications may be made therein without departing from thescope of the invention. For instance it frequently happens that theemulsion to be dehydrated is produced in some refining process fromwhich it is obtained under-a high pressure and in an already heatedcondition so that it contains sufficient heat to vaporize all of itscontained water. If such is the case, further heating in the presentprocess is unnecessary, the heating and pressure producing means ofsu-ch process in .which the heated emulsion is produced being consideredas the equivalents of the pump 3 and heater -4 heretofore described, andthe heated emulsion from such process under suflicient pressure toprevent vaporization of its contained water may flow directly from suchprocess to the pressure reducing valve 5 and be expanded therethroughinto the zone 6in the manner heretofore described.

From the following it will be observed that certain conditions ofpressure drop and size of the orice are required for satisfactory foambreaking, and that departure from these conditions preventsaccomplishing the result sought.

. Pressure Diam. of Test No. orifice in drgigoqs AObservations l whoslbs/sq. in.

,l 1.7 Some very flue foam.

. .1A 2. 3 Very little foam.

'Pte 1.8 Less than A. 362 2. 5 No foam. 1.9 Less than A. Sii e 350 Nofoam. z 2. 7 Do. %2 6.5 D0. 52 19. 5 Coarse foam.

From the foregoing description and examples, it will be apparent thattoo great a pressure drop across the orifice does not effect anymaterial breaking of the foam, and that too low a pressure drop likewisehas little effect on the foam, the critical range of pressure drop beingapparently between 2 to 14 pounds per square inch. The size of theorifice across which the foam is expanded may be varied in reasonablywide limits. For materials of the nature of asphalt, it has been foundthat the orifice should preferably be between 116 and 1/4 inch indiameter, although orifices beyond these limits have been used withsatisfactory results on such materials. With other materials ofdifferent viscosity and surface tension other sizes may be optimum. Itis also desirable that the orifices be not spaced too closely togetherin the orifice plates, a spacing of twice thediameter of the orificesbeing preferably used.

While the invention has been described in connection with its use indehydrating emulsions of heavy hydrocarbon oils such as asphalt, it isto be understood that it is equally applicable to the dehydrating ofother viscous liquids having a tendency to form foam on heating. It isalso to be understood that the principles of the present invention maybeused for breaking foam regardless of how the foam is formed.

For example in various solvent refining processes in which a relativelyviscous liquid is treated with a relatively volatile solvent and theraffinate or extract is then heated to vaporize the solvent, there isfrequently a tendency to form foam. Such mixtures of volatile solventsand viscous liquids, having a tendency to form foam on heating, may beconsidered as the equivalents of the emulsion of water and asphalt here#tofore described `and the principles of the present invention may *beused in separating them.

Having now described our inventiony what We claim and desire to protectby Letters Patent is:

1. A method of removing a relatively volatile liquid from a mixture ofsuch volatile liquid and a viscous liquid, having a tendency to foam onheating, which comprises flowing the mixture through three zones inwhich it is under progressively decreasing pressures, subjecting themixture in the first zone to a temperature suiiiciently above theboiling point of the volatile liquid in the`second zone to effect itssubstantially complete vaporization in the second zone but under apressure suiiiciently high to prevent such vaporization in the firstzone, expanding the mixture into the second intermediate pressure zoneat a pressure sufficientlyv below the pressure in the heating zone tocause substantially all said volatile liquid to vaporize and form withthe viscous liquid a foam, and then expanding the foam through one ormore small orifices into the third lowest pressure zone to thereby breakthe foam into its component parts, the

, vapors of the volatile liquid therein separating from the viscousliquid.

2. A method of removing a relatively volatile liquid from a mixture ofsuch volatile liquid and a viscous liquid; having a tendency to foam onheating, which comprises flowing the mixture through three zones inwhich it is under progressively decreasing pressures, subjecting themixture in the first zone to a temperature suiciently above' the boilingpoint of the volatile liquid in the second zone to effect itssubstantially complete vaporization in the second Zone but under apressure suiiiclently high to prevent such vaporization in the firstzone, expanding the mixture into the second intermediate pressure zoneat a pressure sufliclently below the pressure in the heating zone tocause substantially all said volatile liquid to vaporize and form withthe viscous liquid a foam, and then expanding the foam through a numberof `small orlilces into the third lowest pressure zone to thereby breakthe foam into its component parts, and varying the number of such oricesto thereby variably predetermine the pressure drop between" the secondand third zones.

3. The method set forth in claim 1in which the pressure drop between theilrst and second zones is multiple times that between the second andthird zones.

4. The method set forth in claim 1 in which the pressure drop betweenthe rst and second zones is multiple times that between the second andthird zones and in which the pressure drop between the second and thirdzones is not less than two pounds to the square inch but not more thanabout one atmosphere.

5- 'Ihe process set forth in claim 1 in which the viscous liquid isasphalt and the relatively volatile liquid is water.

6. The method set forth in claim 1 in which the pressure drop betweenthe first and second zones is multiple times that between the second andthird zones and in which the viscous liquid is asphalt and therelatively volatile liquid water.

WIIMER E. MCCORQUODALE, Jn. CHARLES H. BROOKS.

